Patients with hyperthyroidism often exhibit signs and symptoms of anxiety, making it reasonable to question the role of thyroid dysfunction in individuals with anxiety disorders. We have shown that patients with panic disorder and patients with social phobia have normal peripheral thyroid indices, normal rates of antithyroid antibodies, and normal TSH responses to TRH. In addition, we have found that patients with panic disorder have normal Qkd intervals, a putative measure of thyroid hormone effect. These studies indicate that thyroid dysfunction is unlikely to be directly related to the pathogenesis of either panic disorder or social phobia.